Self-limiting and confining epitaxial nucleation

ABSTRACT

A method of fabricating a semiconductor device includes forming a fin in a substrate and depositing a spacer material on the fin. The method includes recessing the spacer material so that a surface of the fin is exposed. The method includes removing a portion of the fin within lateral sidewalls of the spacer material to form a recess, leaving a portion of the fin on the lateral sidewalls. The method further includes depositing a semiconductor material within the recess.

BACKGROUND

The present invention generally relates to fabrication methods andresulting structures for semiconductor devices. More specifically, thepresent invention relates to self-limiting and confining epitaxialnucleation.

Semiconductor devices are formed using active regions of a wafer. Theactive regions are defined by isolation regions used to separate andelectrically isolate adjacent semiconductor devices. For example, in anintegrated circuit having a plurality of metal oxide semiconductor fieldeffect transistors (MOSFETs), each MOSFET has a source and a drain thatare formed in an active region of a semiconductor layer by implantingn-type or p-type impurities in the layer of semiconductor material.Disposed between the source and the drain is a channel (or body) region.Disposed above the body region is a gate electrode. The gate electrodeand the body are spaced apart by a gate dielectric layer.

SUMMARY

Embodiments of the present invention are directed to a method forfabricating a semiconductor device. A non-limiting example of the methodincludes forming a fin in a substrate and depositing a spacer materialon the fin. The method includes recessing the spacer material so that asurface of the fin is exposed. The method includes removing a portion ofthe fin within lateral sidewalls of the spacer material to form arecess, leaving a portion of the fin on the lateral sidewalls. Themethod further includes depositing a semiconductor material within therecess.

Another non-limiting example of the method includes forming a nanosheetstack on a substrate and depositing a spacer material on the nanosheetstack. The method includes recessing the spacer material so that asurface of the nanosheet stack is exposed. The method includes removinga portion of the nanosheet stack within lateral sidewalls of the spacermaterial to form a recess, leaving a portion of the nanosheet stack onthe lateral sidewalls. The method further includes depositing asemiconductor material within the recess.

Embodiments of the invention are directed to a semiconductor device. Anon-limiting example of the semiconductor device includes a finpatterned in a substrate and isolation regions arranged on the substrateand around the fin. The semiconductor device includes a spacer arrangedover the fin, with a portion of the fin lining a lateral sidewall of thespacer. The semiconductor device includes a tapered recess arrangedwithin the fin and a semiconductor material arranged within the taperedrecess.

Additional technical features and benefits are realized through thetechniques of the present invention. Embodiments and aspects of theinvention are described in detail herein and are considered a part ofthe claimed subject matter. For a better understanding, refer to thedetailed description and to the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The specifics of the exclusive rights described herein are particularlypointed out and distinctly claimed in the claims at the conclusion ofthe specification. The foregoing and other features and advantages ofthe embodiments of the invention are apparent from the followingdetailed description taken in conjunction with the accompanying drawingsin which:

FIGS. 1A-6B depict a method for fabricating a semiconductor deviceaccording to embodiments of the invention, in which:

FIG. 1A depicts a cross-sectional side view of a semiconductor deviceafter forming a fin according to embodiments of the invention;

FIG. 1B depicts a top view of the semiconductor device shown in FIG. 1A;

FIG. 2A depicts a cross-sectional side view after depositing a spacermaterial on the fin;

FIG. 2B depicts a top view of the semiconductor device shown in FIG. 2A;

FIG. 3A depicts a cross-sectional side view after partially recessingthe spacer material;

FIG. 3B depicts a top view of the semiconductor device shown in FIG. 3B;

FIG. 4A depicts a cross-sectional side view after recessing the fin;

FIG. 4B depicts a top view of the semiconductor device shown in FIG. 4A;

FIG. 5A depicts a cross-sectional side view after performing anepitaxial growth process according to one or more embodiments;

FIG. 5B depicts a cross-sectional side view after performing anepitaxial growth process according to one or more embodiments;

FIG. 6A depicts a cross-sectional side view after depositing a metalaccording to one or more embodiments; and

FIG. 6B depicts a cross-sectional side view after depositing a metalaccording to one or more embodiments;

FIGS. 7-12B depict a method of fabricating a semiconductor deviceaccording to embodiments of the invention, in which:

FIG. 7 depicts a cross-sectional side view of a semiconductor deviceafter forming a fin according to embodiments of the invention;

FIG. 8 depicts a cross-sectional side view after depositing a spacermaterial on the fin;

FIG. 9 depicts a cross-sectional side view after partially recessing thespacer material;

FIG. 10 depicts a cross-sectional side view after recessing the fin;

FIG. 11A depicts a cross-sectional side view after performing anepitaxial growth process according to one or more embodiments;

FIG. 11B depicts a cross-sectional side view after performing anepitaxial growth process according to one or more embodiments;

FIG. 12A depicts a cross-sectional side view after depositing a metalaccording to one or more embodiments; and

FIG. 12B depicts a cross-sectional side view after depositing a metalaccording to one or more embodiments.

The diagrams depicted herein are illustrative. There can be manyvariations to the diagram or the operations described therein withoutdeparting from the spirit of the invention. For instance, the actionscan be performed in a differing order or actions can be added, deletedor modified. Also, the term “coupled” and variations thereof describeshaving a communications path between two elements and does not imply adirect connection between the elements with no interveningelements/connections between them. All of these variations areconsidered a part of the specification.

In the accompanying figures and following detailed description of thedescribed embodiments, the various elements illustrated in the figuresare provided with two or three digit reference numbers. With minorexceptions, the leftmost digit(s) of each reference number correspond tothe figure in which its element is first illustrated.

DETAILED DESCRIPTION

For the sake of brevity, conventional techniques related tosemiconductor device and integrated circuit (IC) fabrication may or maynot be described in detail herein. Moreover, the various tasks andprocess steps described herein can be incorporated into a morecomprehensive procedure or process having additional steps orfunctionality not described in detail herein. In particular, varioussteps in the manufacture of semiconductor devices andsemiconductor-based ICs are well known and so, in the interest ofbrevity, many conventional steps will only be mentioned briefly hereinor will be omitted entirely without providing the well-known processdetails.

Turning now to an overview of technologies that are more specificallyrelevant to aspects of the invention, one particularly advantageous typeof MOSFET is known generally as a fin-type field effect transistor(FinFET). The basic electrical layout and mode of operation of FinFET donot differ significantly from a traditional field effect transistor. Incontrast to a planar MOSFET, however, source, drain, and channel arebuilt as a three-dimensional bar on top of local shallow trenchisolation (STI) region and semiconductor substrate. Thethree-dimensional bar is the aforementioned “fin,” which serves as thebody of the device. The gate electrode is then wrapped over the top andsides of the fin, and the portion of the fin that is under the gateelectrode functions as the channel. The source and drain regions are theportions of the fin on either side of the channel that are not under thegate electrode. The source and drain regions can be suitably doped toproduce the desired FET polarity, as is known in the art. The dimensionsof the fin establish the effective channel length for the transistor.

Another particularly advantageous type of MOSFET is known generally as agate-all-around (GAA) nanosheet FET, which provides a relatively smallFET footprint by forming the channel region as a series of nanosheets.In a GAA configuration, a nanosheet-based FET includes a source region,a drain region and stacked nanosheet channels between the source anddrain regions. A gate surrounds the stacked nanosheet channels andregulates electron flow through the nanosheet channels between thesource and drain regions. GAA nanosheet FETs are fabricated by formingalternating layers of channel nanosheets and sacrificial nanosheets,which are formed in a stack and then patterned in the shape of a fin.The sacrificial nanosheets are released from the channel nanosheetsbefore the FET device is finalized. For n-type FETs, the channelnanosheets are silicon (Si), and the sacrificial nanosheets are silicongermanium (SiGe). For p-type FETs, the channel nanosheets are either Siwith sacrificial SiGe, or the channel nanosheets are SiGe withsacrificial Si.

Epitaxially grown material is used to form source/drain regions ofFinFETs and nanosheet FETs. Forming epitaxially grown material to asubstantially uniform height in these regions can be challenging.Epitaxially grown materials can have heights that are highly variable,even when the same process is used in the same region of a device, whichcan increase the fringe capacitance of the device.

Turning now to an overview of the aspects of the invention, one or moreembodiments of the invention address the above-described shortcomings ofthe prior art by providing a method that confines the epitaxial growthwithin sidewall spacers so that the epitaxial growth does not growlaterally and is self-limited vertically. After forming lateral sidewallspacers on the fins (of both FinFET devices and nanosheet devices), thefins are recessed within the fin in a deep “v-shape,” and the epitaxialgrowth is applied to confine the growth to the area of the original fin.

The above-described aspects of the invention address the shortcomings ofthe prior art by confining the epitaxial growth of source/drain regionswithin lateral spacers to mitigate non-uniform lateral and verticalgrowth on the fins. The v-shaped epitaxial growth extends vertically andin a substantially uniform manner. The resulting epitaxial growthreduces the fringe capacitance, and the v-shaped epitaxial growth canincrease the contact area, thereby reducing contact resistance.

Turning now to a more detailed description of aspects of the presentinvention, FIGS. 1A-6B depict a method for fabricating a semiconductordevice according to embodiments of the invention. FIG. 1A depicts across-sectional side view of a semiconductor device after forming a fin106 according to embodiments of the invention. FIG. 1B depicts a topview of the semiconductor device shown in FIG. 1A.

The semiconductor device is a nanosheet FET and includes isolationregions 103 arranged on a semiconductor substrate 101 and around the fin106. The isolation regions 103 are for isolation of active areas fromone another.

Non-limiting examples of suitable substrate 101 materials include Si(silicon), strained Si, SiC (silicon carbide), Ge (germanium), SiGe(silicon germanium), SiGeC (silicon-germanium-carbon), Si alloys, Gealloys, III-V materials (e.g., GaAs (gallium arsenide), InAs (indiumarsenide), InP (indium phosphide), or aluminum arsenide (AlAs)), II-VImaterials (e.g., CdSe (cadmium selenide), CdS (cadmium sulfide), CdTe(cadmium telluride), ZnO (zinc oxide), ZnSe (zinc selenide), ZnS (zincsulfide), or ZnTe (zinc telluride)), or any combination thereof.

The isolation regions 103 can be formed by any known method in the art,including, for example, lithography or etching to form trenches, andthen filling the trenches with an insulating material, such as silicondioxide. In the exemplary embodiment, the isolation regions 103 areshallow trench isolation regions (STIs). However, the isolation region103 can be a trench isolation region, a field oxide isolation region(not shown), or any other equivalent known in the art. The isolationregions 103 can provide isolation between neighboring active regions andcan be used when the neighboring active regions have oppositeconductivities, i.e., nFETs and pFETs. As such, the at least oneisolation region 103 can separate an nFET device region from a pFETdevice region. The isolation region 103 can also provide isolationbetween the source and the drain of a FinFET or nanosheet device when itis located between two fins or nanosheets in the same device type. nFETor pFET devices with multiple fins or nanosheets per active area havethe isolation region 103 located between fins or nanosheets.

A fin 106 is patterned in the substrate 101. Spacers 102 can be formedaround the fins 106 within the isolation regions 102. Non-limitingexamples of suitable materials for the spacers 102 include dielectricoxides (e.g., silicon oxide), dielectric nitrides (e.g., siliconnitride), dielectric oxynitrides, or any combination thereof. The spacermaterial is deposited by a deposition process, for example, chemicalvapor deposition (CVD) or physical vapor deposition (PVD). The spacermaterial can be etched by a dry etch process, for example, a RIEprocess.

The fin 106 includes a nanosheet stack 120. Although a single fin 106and nanosheet stack 120 is shown an exemplary embodiment, thesemiconductor device can include any number of fins 106 and nanosheetstacks 120, such as a plurality of fins and nanosheet stacks in otherembodiments. The fin 106 and nanosheet stack 120 can be formed in thesubstrate 101 by patterning a mask and then etching the substrate 101.The fin 106 and nanosheet stacks 120 also can be patterned in thesubstrate by, for example, sidewall imaging transfer or direct printextreme ultraviolet lithography.

The nanosheet stack 120 extends over the isolation regions 103 andincludes alternating layers of a first nanosheet 110 and a secondnanosheet 111. The first nanosheet 110 is a semiconductor material, forexample, silicon germanium in some embodiments. Other non-limitingexamples of semiconductor materials for the first nanosheet 110 includeSi (silicon), strained Si, SiC (silicon carbide), Ge (germanium), SiGeC(silicon-germanium-carbon), Si alloys, Ge alloys, GaAs (galliumarsenide), InAs (indium arsenide), InP (indium phosphide), or anycombination thereof.

The second nanosheet 111 alternates with the first nanosheet 110 in thenanosheet stack 120. The second nanosheet 111 is a semiconductormaterial, for example, silicon. Other non-limiting examples ofsemiconductor materials for the second nanosheet 111 include strainedSi, SiC (silicon carbide), Ge (germanium), SiGe (silicon germanium),SiGeC (silicon-germanium-carbon), Si alloys, Ge alloys, GaAs (galliumarsenide), InAs (indium arsenide), InP (indium phosphide), or anycombination thereof.

Although nanosheet stack 120 includes four layers each of firstnanosheet 110 and second nanosheet 111, the nanosheet stack 120 caninclude any number of first nanosheets 110 and second nanosheets 111.The nanosheet stack 120 can include one or more layers of each of firstnanosheet 110 and second nanosheet 111. For example, nanosheet stack 120can include one layer of first nanosheet 110 and one layer of secondnanosheet 111 disposed on the first nanosheet 110.

First and second nanosheets 110 and 111 can be formed on the substrate101 by for example, forming alternating layers of first and secondnanosheets 110 and 111 on the substrate 101, patterning the multi-layerstack into fin shaped structures, with the width of the fin 106structures defining the width of the nanosheets. The height of thenanosheet stack 120 generally vary, as it depends on the type of device,and is not intended to be limited.

A gate 130 is arranged on the nanosheet stack 120, as shown in FIG. 1B.The gate 110 is a “dummy gate” according to one or more embodiments andincludes a sacrificial gate material (dummy gate material). Thesacrificial gate material can be, for example, amorphous silicon,polysilicon, amorphous carbon, a dielectric silicon dioxide, or asilicon nitride material.

The gate is an active metal gate according to one or more embodiments.The metal gate includes metal gates formed, for example, by filling adummy gate opening (after removing the sacrificial gate material) withone or more dielectric materials, one or more workfunction metals, andone or more metal gate conductor materials. The gate dielectricmaterial(s) can be a dielectric material having a dielectric constantgreater than about 3.9, about 7.0, or about 10.0. Non-limiting examplesof suitable materials for the dielectric material include oxides,nitrides, oxynitrides, silicates (e.g., metal silicates), aluminates,titanates, nitrides, or any combination thereof. Examples of high-kmaterials (with a dielectric constant greater than 7.0) include, but arenot limited to, metal oxides such as hafnium oxide, hafnium siliconoxide, hafnium silicon oxynitride, lanthanum oxide, lanthanum aluminumoxide, zirconium oxide, zirconium silicon oxide, zirconium siliconoxynitride, tantalum oxide, titanium oxide, barium strontium titaniumoxide, barium titanium oxide, strontium titanium oxide, yttrium oxide,aluminum oxide, lead scandium tantalum oxide, and lead zinc niobate. Thehigh-k material can further include dopants such as, for example,lanthanum and aluminum.

The work function metal(s) can be disposed over the gate dielectricmaterial. The type of work function metal(s) depends on the type oftransistor and can differ between an nFET and a pFET. Non-limitingexamples of suitable work function metals include p-type work functionmetal materials and n-type work function metal materials. P-type workfunction materials include compositions such as ruthenium, palladium,platinum, cobalt, nickel, and conductive metal oxides, or anycombination thereof. N-type metal materials include compositions such ashafnium, zirconium, titanium, tantalum, aluminum, metal carbides (e.g.,hafnium carbide, zirconium carbide, titanium carbide, and aluminumcarbide), aluminides, or any combination thereof. The work functionmetal(s) can be deposited by a suitable deposition process, for example,CVD, PECVD, PVD, plating, thermal or e-beam evaporation, and sputtering.

A conductive metal is deposited over the dielectric material(s) andworkfunction layer(s) to form the metal gate. Non-limiting examples ofsuitable conductive metals include aluminum (Al), platinum (Pt), gold(Au), tungsten (W), titanium (Ti), or any combination thereof. Theconductive metal can be deposited by a suitable deposition process, forexample, CVD, PECVD, PVD, plating, thermal or e-beam evaporation, andsputtering.

The gate 130 includes gate spacers 131. The gate spacers 131 include adielectric material, for example, silicon dioxide, silicon nitride,SiOCN, or SiBCN. Other non-limiting examples of materials for the gatesspacers 131 include dielectric oxides, dielectric nitrides, dielectricoxynitrides, or any combination thereof.

FIG. 2A depicts a cross-sectional side view after depositing a spacermaterial 202 on the nanosheet stack 120 of the fin 106. FIG. 2B depictsa top view of the semiconductor device shown in FIG. 2A.

The spacer material 202 covers and surrounds exposed areas of thenanosheet stack 120 that extends from the fin 106. The spacer material202 is a dielectric material. According to one or more embodiments, thespacer material 202 is a low-k dielectric material. The low-k spacermaterial can include Si, N, and at least one element selected from thegroup consisting of C and B. Additionally, the low-k spacer material cancontain Si, N, B, and C, and O. For example, the low-k spacer materialcan include SiBN, SiCN, SiBCN, SiOCN, SiON, or any combination thereof.

FIG. 3A depicts a cross-sectional side view after partially recessingthe spacer material 202. FIG. 3B depicts a top view of the semiconductordevice shown in FIG. 3B.

The spacer material 202 is partially recessed such that a top surface ofthe nanosheet stack 120 of the fin 106 is exposed. According to one ormore embodiments, the etch process is a dry etch process and/or a wetetch process. According to some embodiments, the etch process used topartially recess the spacer material 202 is a reactive ion etch (RIE)process.

FIG. 4A depicts a cross-sectional side view after further recessing thefin 106. FIG. 4B depicts a top view of the semiconductor device shown inFIG. 4A.

Once exposed, the fin 106 is further etched to remove a portion of thefin 106 below the level of the isolation regions 103. A portion of thenanosheet stack 120 and a portion of the fin 106 in the substrate 101are removed. A directional etch is performed to form a v-shaped oru-shaped recess 403 in the fin 106. The recess 403 has sidewalls thatare angled at an oblique angle with respect to an axis perpendicular tothe substrate 101. The directional etch forms a tapered cavity 444(recess or opening) between the lateral sidewalls of the spacer material202, which removes a majority of the nanosheet stack 120 material butleaves portions 440 of the nanosheet stack 120 on lateral sidewalls ofthe spacer material 202. The inner sidewalls of the tapered cavity 444are not parallel to one another and can be arranged at any angle withrespect to the normal axis to the horizontal substrate 101.

According to one or more embodiments, the directional etch is a RIEprocess. The RIE process can employ polymerization during the RIE. TheRIE process also can be a crystal orientation dependent RIE. Theresulting profile of the tapered cavity 444 is related to the fin ornanosheet profile. The fin or nanosheet profile is tapered naturally dueto the non-ideality of the ME process used to pattern fins ornanosheets. The fin or nanosheet profile taper can be adjusted with theRIE depth or RIE process conditions (pressure, bias, etc.). Thecombination of the tapered fin or nanosheet profile and directionalcavity ME leaves slivers of semiconductor material on the sidewalls ofthe spacer material.

Following the directional etch shown in FIGS. 4A and 4B, an epitaxialgrowth process can be performed, as shown in FIG. 5A or 5B. FIG. 5Adepicts a cross-sectional side view after performing an epitaxial growthprocess according to one or more embodiments. FIG. 5B depicts across-sectional side view after performing an epitaxial growth processaccording to one or more embodiments.

An epitaxial growth process is performed to deposit a crystallinesemiconductor material 505 onto a crystalline substrate beneath. Thedeposited semiconductor material will grow from the semiconductormaterial of the substrate 101 at the recess 403 (see FIG. 4A). Leaving aportion 440 of the nanosheet stack 120 on the sidewalls of the spacermaterial 202 also allows the deposited semiconductor material to growfrom the lateral sidewalls within the spacer material 202.

The terms “epitaxial growth and/or deposition” and “epitaxially formedand/or grown” mean the growth of a semiconductor material on adeposition surface of a semiconductor material, in which thesemiconductor material being grown has the same crystallinecharacteristics as the semiconductor material of the deposition surface.In an epitaxial deposition process, the chemical reactants arecontrolled and the system parameters are set so that the depositingatoms arrive at the deposition surface of the semiconductor substratewith sufficient energy to move around on the surface and orientthemselves to the crystal arrangement of the atoms of the depositionsurface. Therefore, an epitaxial semiconductor material has the samecrystalline characteristics as the deposition surface on which it isformed.

According to exemplary embodiments, an epitaxial semiconductor materialdeposited on a {100} crystal surface will take on a {100} orientation.According to other exemplary embodiments, an epitaxial semiconductormaterial deposited on a {111} crystal surface will take on a {111}orientation. In some embodiments, epitaxial growth and/or depositionprocesses are selective to forming on semiconductor surface, and do notdeposit material on dielectric surfaces, such the spacer material 202.

The processing parameters used to form the semiconductor material 505,such as temperature, pressure, acid concentration, among others, can bevaried such that the semiconductor material 505 substantially fills theopen recessed area within the spacer material 202, as shown in FIG. 5A,or such that the semiconductor material 505 forms a tapered opening 601(or void) as shown in FIG. 5B. When the semiconductor material 505 isovergrown using epitaxial growth processes (FIG. 5A), the semiconductormaterial 505 substantially fills the area within the spacer material202. The tapered opening 501 is formed when the semiconductor material505 is not overgrown, as it can pinch off to form the v-shaped opening501.

Epitaxial layers can be grown from gaseous or liquid precursors.Epitaxial growth can be deposited using vapor-phase epitaxy (VPE),molecular-beam epitaxy (MBE), liquid-phase epitaxy (LPE), or othersuitable process. The epitaxial silicon, silicon germanium, and/orcarbon doped silicon (Si:C) can be doped during deposition by adding adopant or impurity to form a silicide. The silicon can be doped with ann-type dopant (e.g., phosphorus, arsenic, or antimony) or a p-typedopant (e.g., boron), depending on the type of transistor.

FIG. 6A depicts a cross-sectional side view after depositing a metal 601on the semiconductor material 505 shown in FIG. 5A. FIG. 6B depicts across-sectional side view after depositing a metal 601 on thesemiconductor material 505 shown in FIG. 5B.

The metal 601 surrounds the spacer material 202 and covers thesemiconductor material 505 to form a source/drain contact. When atapered opening is formed in the semiconductor material 505 (FIG. 6B),the metal 601 fills the opening which increases the contact area toreduce contact resistance. Optionally (not shown), the spacer material202 can be selectively removed before metal 601 deposition to increasethe contact area with the sidewalls and reduce contact resistance.

The metal 601 optionally includes a metal silicide film arrangeddirectly on the semiconductor material 505, followed by a conductivemetal fill. The metal silicide film can be formed by performing athermal treatment to a metallic film. The metallic film can be depositedby performing an evaporation process or a sputtering process. Themetallic film is then annealed by heating inside a furnace or performinga rapid thermal treatment in an atmosphere that includes pure inertgases (e.g., nitrogen or argon). Non-limiting examples of suitable metalsilicide materials include titanium silicide, tungsten silicide, cobaltsilicide, nickel silicide, molybdenum silicide, platinum silicide, orany combination thereof.

The conductive metal can be, but is not limited to, aluminum (Al),cobalt (Co), platinum (Pt), gold (Au), tungsten (W), titanium (Ti), orany combination thereof. The conductive material can be deposited by asuitable deposition process, for example, CVD, PECVD, PVD, plating,thermal or e-beam evaporation, or sputtering.

FIGS. 7-12B depict a method of fabricating a semiconductor deviceaccording to embodiments of the invention. FIG. 7 depicts across-sectional side view of a semiconductor device after forming a finaccording to embodiments of the invention.

The semiconductor device is a FinFET and includes isolation regions 103arranged on a semiconductor substrate 101. The isolation regions 103 arefor isolation of active areas from one another.

A fin 706 is patterned in the substrate 101. Spacers 102 can be formedaround the fins 106 within the isolation regions 103. Although a singlefin 706 is shown an exemplary embodiment, the semiconductor device caninclude any number of fins 706, such as a plurality of fins in otherembodiments. The fin 706 can be formed in the substrate 101 bypatterning a mask and then etching the substrate 101. The fin 106 alsocan be patterned in the substrate 101 by, for example, sidewall imagingtransfer.

A gate 130 is arranged on the fin 706, as shown in FIG. 1B. The gate 110is a “dummy gate” according to one or more embodiments and includes asacrificial gate material (dummy gate material). The gate is an activemetal gate according to one or more embodiments.

FIG. 8 depicts a cross-sectional side view after depositing a spacermaterial 202 on the fin 706. The spacer material 202 covers andsurrounds the exposed areas of the fin 706. The spacer material 202 is adielectric material. According to one or more embodiments, the spacermaterial 202 is a low-k dielectric material.

FIG. 9 depicts a cross-sectional side view after partially recessing thespacer material 202. The spacer material 202 is partially recessed suchthat a top surface of the fin 706 is exposed. According to one or moreembodiments, the etch process is a dry etch process and/or a wet etchprocess. According to some embodiments, the etch process used topartially recess the spacer material 202 is a reactive ion etch (RIE)process.

FIG. 10 depicts a cross-sectional side view after further recessing thefin 706. Once exposed, the fin 706 is further etched to remove a portionof the fin 706 from between the lateral sidewalls of the spacer material202 and further below the spacer material 202. A directional etch isperformed to form a v-shaped or u-shaped recess 403 in the fin 706. Therecess 403 has sidewalls that are angled at oblique angles with respectto an axis perpendicular to the substrate 101. The directional etchforms a tapered cavity 444 between the walls of the spacer material 202,which removes a majority of the fin 706 material but leaves portions 440of the fin 706 on lateral sidewalls of the spacer material 202. Theinner sidewalls of the tapered cavity 444 are not parallel to oneanother and can be arranged at any angle with respect to the normal axisto the horizontal substrate 101.

Following the directional etch shown in FIG. 10, an epitaxial growthprocess can be performed, as shown in FIGS. 11A and 11B. FIG. 11Adepicts a cross-sectional side view after performing an epitaxial growthprocess according to one or more embodiments. FIG. 11B depicts across-sectional side view after performing an epitaxial growth processaccording to one or more embodiments.

An epitaxial growth process is performed to deposit a crystallinesemiconductor material 505 onto a crystalline substrate beneath. Thedeposited semiconductor material will grow from the semiconductormaterial of the substrate 101 at the recess 403 (see FIG. 10). Leaving aportion 440 of the fin 706 on the sidewalls of the spacer material 202also allows the deposited semiconductor material to grow from thelateral sidewalls within the spacer material 202.

The processing parameters used to form the semiconductor material 505,such as temperature, pressure, acid concentration, among others, can bevaried such that the semiconductor material 505 substantially fills theopen recessed area within the spacer material 202, as shown in FIG. 11A,or such that the semiconductor material 505 forms a tapered opening 601(or void) as shown in FIG. 11B. When the semiconductor material 505 isovergrown using epitaxial growth processes (FIG. 11A), the semiconductormaterial 505 substantially fills the area within the spacer material202. The tapered opening 501 is formed when the semiconductor material505 is not overgrown, as it can pinch off to form the v-shaped opening501.

FIG. 12A depicts a cross-sectional side view after depositing a metal601 on the semiconductor material 505 shown in FIG. 11A. FIG. 12Bdepicts a cross-sectional side view after depositing a metal 601 on thesemiconductor material 505 shown in FIG. 11B.

The metal 601 surrounds the spacer material 202 and covers thesemiconductor material 505 to form a source/drain contact. When atapered opening is formed in the semiconductor material 505 (FIG. 11B),the metal 601 fills the opening which increases the contact area toreduce contact resistance. Optionally (not shown), the spacer material202 can be selectively removed before metal 601 deposition to increasethe contact area with the sidewalls and reduce contact resistance.

The metal 601 optionally includes a metal silicide film arrangeddirectly on the semiconductor material 505, followed by a conductivemetal fill.

Various embodiments of the present invention are described herein withreference to the related drawings. Alternative embodiments can bedevised without departing from the scope of this invention. Althoughvarious connections and positional relationships (e.g., over, below,adjacent, etc.) are set forth between elements in the followingdescription and in the drawings, persons skilled in the art willrecognize that many of the positional relationships described herein areorientation-independent when the described functionality is maintainedeven though the orientation is changed. These connections and/orpositional relationships, unless specified otherwise, can be direct orindirect, and the present invention is not intended to be limiting inthis respect. Accordingly, a coupling of entities can refer to either adirect or an indirect coupling, and a positional relationship betweenentities can be a direct or indirect positional relationship. As anexample of an indirect positional relationship, references in thepresent description to forming layer “A” over layer “B” includesituations in which one or more intermediate layers (e.g., layer “C”) isbetween layer “A” and layer “B” as long as the relevant characteristicsand functionalities of layer “A” and layer “B” are not substantiallychanged by the intermediate layer(s).

The following definitions and abbreviations are to be used for theinterpretation of the claims and the specification. As used herein, theterms “comprises,” “comprising,” “includes,” “including,” “has,”“having,” “contains” or “containing,” or any other variation thereof,are intended to cover a non-exclusive inclusion. For example, acomposition, a mixture, process, method, article, or apparatus thatcomprises a list of elements is not necessarily limited to only thoseelements but can include other elements not expressly listed or inherentto such composition, mixture, process, method, article, or apparatus.

Additionally, the term “exemplary” is used herein to mean “serving as anexample, instance or illustration.” Any embodiment or design describedherein as “exemplary” is not necessarily to be construed as preferred oradvantageous over other embodiments or designs. The terms “at least one”and “one or more” are understood to include any integer number greaterthan or equal to one, i.e. one, two, three, four, etc. The terms “aplurality” are understood to include any integer number greater than orequal to two, i.e. two, three, four, five, etc. The term “connection”can include an indirect “connection” and a direct “connection.”

References in the specification to “one embodiment,” “an embodiment,”“an example embodiment,” etc., indicate that the embodiment describedcan include a particular feature, structure, or characteristic, butevery embodiment may or may not include the particular feature,structure, or characteristic. Moreover, such phrases are not necessarilyreferring to the same embodiment. Further, when a particular feature,structure, or characteristic is described in connection with anembodiment, it is submitted that it is within the knowledge of oneskilled in the art to affect such feature, structure, or characteristicin connection with other embodiments whether or not explicitlydescribed.

For purposes of the description hereinafter, the terms “upper,” “lower,”“right,” “left,” “vertical,” “horizontal,” “top,” “bottom,” andderivatives thereof shall relate to the described structures andmethods, as oriented in the drawing figures. The terms “overlying,”“atop,” “on top,” “positioned on” or “positioned atop” mean that a firstelement, such as a first structure, is present on a second element, suchas a second structure, wherein intervening elements such as an interfacestructure can be present between the first element and the secondelement. The term “direct contact” means that a first element, such as afirst structure, and a second element, such as a second structure, areconnected without any intermediary conducting, insulating orsemiconductor layers at the interface of the two elements.

The phrase “selective to,” such as, for example, “a first elementselective to a second element,” means that the first element can beetched and the second element can act as an etch stop.

The terms “about,” “substantially,” “approximately,” and variationsthereof, are intended to include the degree of error associated withmeasurement of the particular quantity based upon the equipmentavailable at the time of filing the application. For example, “about”can include a range of ±8% or 5%, or 2% of a given value.

As previously noted herein, for the sake of brevity, conventionaltechniques related to semiconductor device and integrated circuit (IC)fabrication may or may not be described in detail herein. By way ofbackground, however, a more general description of the semiconductordevice fabrication processes that can be utilized in implementing one ormore embodiments of the present invention will now be provided. Althoughspecific fabrication operations used in implementing one or moreembodiments of the present invention can be individually known, thedescribed combination of operations and/or resulting structures of thepresent invention are unique. Thus, the unique combination of theoperations described in connection with the fabrication of asemiconductor device according to the present invention utilize avariety of individually known physical and chemical processes performedon a semiconductor (e.g., silicon) substrate, some of which aredescribed in the immediately following paragraphs.

In general, the various processes used to form a micro-chip that will bepackaged into an IC fall into four general categories, namely, filmdeposition, removal/etching, semiconductor doping andpatterning/lithography. Deposition is any process that grows, coats, orotherwise transfers a material onto the wafer. Available technologiesinclude physical vapor deposition (PVD), chemical vapor deposition(CVD), electrochemical deposition (ECD), molecular beam epitaxy (MBE)and more recently, atomic layer deposition (ALD) among others.Removal/etching is any process that removes material from the wafer.Examples include etch processes (either wet or dry), andchemical-mechanical planarization (CMP), and the like. Semiconductordoping is the modification of electrical properties by doping, forexample, transistor sources and drains, generally by diffusion and/or byion implantation. These doping processes are followed by furnaceannealing or by rapid thermal annealing (RTA). Annealing serves toactivate the implanted dopants. Films of both conductors (e.g.,poly-silicon, aluminum, copper, etc.) and insulators (e.g., variousforms of silicon dioxide, silicon nitride, etc.) are used to connect andisolate transistors and their components. Selective doping of variousregions of the semiconductor substrate allows the conductivity of thesubstrate to be changed with the application of voltage. By creatingstructures of these various components, millions of transistors can bebuilt and wired together to form the complex circuitry of a modernmicroelectronic device. Semiconductor lithography is the formation ofthree-dimensional relief images or patterns on the semiconductorsubstrate for subsequent transfer of the pattern to the substrate. Insemiconductor lithography, the patterns are formed by a light sensitivepolymer called a photo-resist. To build the complex structures that makeup a transistor and the many wires that connect the millions oftransistors of a circuit, lithography and etch pattern transfer stepsare repeated multiple times. Each pattern being printed on the wafer isaligned to the previously formed patterns and slowly the conductors,insulators and selectively doped regions are built up to form the finaldevice.

The flowchart and block diagrams in the Figures illustrate possibleimplementations of fabrication and/or operation methods according tovarious embodiments of the present invention. Variousfunctions/operations of the method are represented in the flow diagramby blocks. In some alternative implementations, the functions noted inthe blocks can occur out of the order noted in the Figures. For example,two blocks shown in succession can, in fact, be executed substantiallyconcurrently, or the blocks can sometimes be executed in the reverseorder, depending upon the functionality involved.

The descriptions of the various embodiments of the present inventionhave been presented for purposes of illustration, but are not intendedto be exhaustive or limited to the embodiments described. Manymodifications and variations will be apparent to those of ordinary skillin the art without departing from the scope and spirit of the describedembodiments. The terminology used herein was chosen to best explain theprinciples of the embodiments, the practical application or technicalimprovement over technologies found in the marketplace, or to enableothers of ordinary skill in the art to understand the embodimentsdescribed herein.

What is claimed is:
 1. A method of fabricating a semiconductor device,the method comprising: forming a fin in a substrate, the fin comprisinga first semiconductor material; depositing a spacer material on the fin;recessing the spacer material so that a surface of the fin is exposed;removing a portion of the fin within lateral sidewalls of the spacermaterial to form a recess, leaving a portion of the first semiconductormaterial of the fin on the lateral sidewalls; and depositing a secondsemiconductor material within the recess.
 2. The method of claim 1,wherein the spacer material comprises a dielectric material.
 3. Themethod of claim 1, wherein the spacer material comprises a low-kmaterial.
 4. The method of claim 1, wherein the spacer materialcomprises SiBN, SiCN, SiBCN, or any combination thereof.
 5. The methodof claim 1, wherein the spacer material surrounds exposed areas of thefin.
 6. The method of claim 1, wherein recessing the spacer materialcomprises a reactive ion etch.
 7. The method of claim 1, wherein therecess comprises a tapered recess.
 8. The method of claim 7, wherein thetapered recess is arranged below a surface of isolation regions.
 9. Themethod of claim 1, wherein depositing the second semiconductor materialcomprises applying an epitaxial growth process.